The present invention relates to a technical field of liquid crystal displays, and more particularly to a TFT device of a liquid crystal display and a manufacturing method therefor.
In a TFT (thin film transistor) liquid crystal display, different metal layers are connected through an ITO (indium tin oxide) transparent conductive film. Because the resistance and impedance of the ITO is much greater than that of metallic aluminum or copper, it causes the contact impedance between different metal layers to be great, and then the display effect is not good in the following process.
Refer now to FIG. 1, which is a cross-sectional structural schematic view of a traditional TFT device of a liquid crystal display (LCD). A scan electrode line 12 is formed on a glass substrate 11; the scan electrode line 12 is covered with a first silicon nitride protective film 13; and a signal electrode line 14 is covered with a second silicon nitride protective film 15. Above the scan electrode line 12, the first silicon nitride protective film 13 and the second silicon nitride protective film 15 are respectively etched to form a first contact hole 16; and above the signal electrode line 14, the second silicon nitride protective film 15 is etched to form a second contact hole 17. After that, an ITO layer 18 is deposited to connect with the different metal layers. In this connecting method, the ITO layer 18 must begin from the first contact hole 16 on the scan electrode line 12, climb the first silicon nitride protective film 13 and the second silicon nitride protective film 15, pass through the second contact hole 17 on the signal electrode line 14, and then connect together the two metal lines. Because the impedance value of the ITO is much greater than that of metallic aluminum or copper, this connecting method will cause the contact impedance to be great, and thereby it can easily occur that the display effect is not good in the following process.
Hence, it is necessary to provide a new TFT device of a liquid crystal display with a different connecting method for metal layers, so as to lower the contact impedance between the metal layers, and increase the product yield rate.